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Post by namic69 on Jun 9, 2004 10:42:05 GMT 11
Can anyone tell me if there is any benefit in installing a 3inch exhaust instead of a 2.5inch?
Can anyone recommend somewhere in Auckland.
A put a 2.5 in exhaust on my 94 and it gave me about 10% more power.
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Post by mudgrip4 on Jun 9, 2004 15:16:30 GMT 11
Hi Namic - just about to put 2.5" pipe from turbo back on my 4JB1 and every enquiry from diesel outfits, exhaust companies and Isuzu owners said clearly don't bother with 3" - no gain, and possible issues fitting it on. Same message from owners here.
A surprisingly big gain in pipe area even with move from standard 2" to 2.5". The 2" (5.08cm) diameter pipe has an area of approx 20.5 cm2 (centimeters squared). The bigger pipe at 2.5" (6.35cm) has an area of about 32 cm2, more than half as big again than the original 2" and that's a massive reduction in back pressure. (if my maths stand up...)
Getting mine from a pipe bender company with mates to put it on. Check to see if your pipe has a flexible joint beside the gearbox. This is to handle engine movement and costs $82-92 extra here - Mike.
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Post by geeves on Jun 9, 2004 15:43:09 GMT 11
An interesting therory Ive heard recently is that the first couple of feet of pipe should remain as standard size as it helps the speed of gas in the turbo at low revs Mine is 2.5 from the flexi joint and the improvment is substantial right through the rev range Aparantly if you go 2.5 or bigger all the way to the turbo then the top end dopes improve to about the same as my setup but the low and mid range can end up worse.
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Post by namic69 on Jun 9, 2004 17:52:17 GMT 11
I have heard the same, my old truck was done from the flex joint as I was told that going from turbo would cause lag issues....
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Post by mudgrip4 on Jun 9, 2004 21:04:11 GMT 11
This is interesting. Alan - what percentage increase in power would you say you have got with the 2.5" from the flexi joint - I think you've got an 89 2.8? so the result is going to be the same for mine. And if I don't have to buy a new flexi joint, that's going to save money. How did you connect the new pipe to the old flexi? How is it fixed there?
Is your percentage consistent across the range? or more at top end etc? I think both Namic and I would appreciate some comments on this from others who've done the job as well before we spend some dollars. Many thanks - Mike.
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Post by namic69 on Jun 10, 2004 4:59:53 GMT 11
I got about 10% over all in my 3.1 94 Bighorn but the big difference was in the sand there was about 15% or so more torque. I am selling my old one so anyone wanting to compare can take it for a spin. Next week tho as am having the turbo replaced under warranty.
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Post by geeves on Jun 10, 2004 17:58:17 GMT 11
Garage fitted the exhaust and I havnt actualy looked to see how its done I think they put a flange there.Before fitting the big exhaust it wouldnt pull before 1800rpm and ran out of steam around 3800 and went up Ngauranga Gorge at 80kph in 4th. With the exhaust done it started pulling from 1500 and pulls hard to the rev limiter arount 4200. Ngauranga gorge is now 85/90kph in 4th . Fitting the snorkle imroved things again although its hard to measure
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Post by geeves on Jun 10, 2004 18:00:36 GMT 11
Also ecconomy improved although the savings would only just pay for the exhaust in the life of the exhaust. If you need to change the exhaust 2.5 inch is definatly the way to go but hard to justify otherwise.
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Post by mudgrip4 on Jun 10, 2004 19:42:58 GMT 11
Sounds good. Looking back through old posts, noted people getting good results with 2.5" from the turbo and also from the flexi joint. Wanted to get clearer picture if possible before I buy so today rang 3 muffler fitting firms. One recommended pipe from flexi joint for 4wds, whil the other 2 always fitted from the turbo! Suggestion was you can get 70-80% effect with 2.5" pipe from the flexi joint and of course its much cheaper - new flexi joints alone $80-160 depending which you buy. Either pipe connection seems to work pretty good.
Then rang 3 4wd upgrade companies to see what they do. All said straight from turbo with no problems experienced with back pressure. From flexi joint good, but from turbo (about twice the price) is better. One comment was that diesels don't suffer so much from loss of back pressure as diesel turbos don't need it as much as petrol turbos. No turbo lag on any diesels they'd done - Toyota, Nissan etc, but if it happens it can be fixed with a cheap blow-off valve apparently - haven't a clue how. But my teenage son would like that option!
One bloke told me to ring a specialist tuning company -Turbo Technology - who did my injection timing advancing and fuel increase (at least 10% hp extra) last year.They said do 2.5" pipes from the turbo - no problems with back pressure. Said if you've had the injection timing advanced and fuel delivery increased you get even better results from a bigger pipe than from standard tuning.
So the bottom line appears to be good results if we add the 2.5" from the flexi joint - and at about half the price. And if you,ve got spare dollars go from the turbo down and you'll get the max benefit. Can get my pipe made and fitted at mates rates so I'll do the whole pipe ex turbo - but - will hang on to the old pipe so can refit the front half if something goes wrong! Will report on results in 2-3 weeks when I have saved enough pennies to have it done - Mike.
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Post by namic69 on Jun 11, 2004 5:35:45 GMT 11
Thanks for that mike good work. I am interested in the advanced timing thing too. More details including cost would be great.
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Post by francesco on Jun 11, 2004 11:56:13 GMT 11
If you can afford the extra $$$ 2.5 from turbo back is definently the way to go.
I had 2.5 from about 1 ft above the the flex back for about 6ths. Just last week I got the rest of the system done and now have full 2.5 from the turbo back. There is a definent increase in torque, 1st and 2nd gear pull harder now. I was plesently surprised. ;D
No sign of lagg
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Post by mudgrip4 on Jun 11, 2004 15:53:07 GMT 11
That's great to hear and confirms the pro opinions. Great to hear no lag. If anyone's doing this, its good to shop aroung a bit for the flexi joint - had quotes of $75 to 160 for this bit (200 mm).
One guy told me his company had fitted 2.5" from the flexi back on hundreds of Surfs with that 2.4 turbo motor that is so bad for cracking heads, and this shorter pipe change fixes the problem - was effective in removing back pressure and heat build-up. So it appears either choice - from flexi joint or turbo back is going to be a good call. I'll definitely do mine ex turbo now. Another small step towards the 500hp bighorn.. Mike.
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Post by francesco on Jun 11, 2004 16:34:41 GMT 11
In the readouts of dynos for the 4jb1-t, which I have.....They managed to get a bit more than 5oo hp from them....and good increase in torque....I hope to post them on the forum soon under the dyno thread.
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RoeDao
Isuzu Junior
If you notice this notice, you will notice that this notice is not worth noticing
Posts: 52
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Post by RoeDao on Dec 9, 2004 19:34:20 GMT 11
i got my 2.5" exhaust done from the turbo back..... they removed that horribly restrictive dump pipe and ran it straight from the turbo to the back through a straight through muffler..... from what i have been told by all and sundry..... the less restriction on a turbo the better, no back pressure is needed...... the turbo will spin up faster if the exhaust can get through quicker. I noticed a huge increase in power and torque straight away! the turbo spins up quicker, and i get less lag. I was told the same about hte 3" exhaust, waste of time because the outlet on the turbo is only 2.5" and it would be a costly waste of money. My bosst went to about 11psi which is 3 psi more than factory standard.
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Post by caffa on Jan 16, 2005 19:11:29 GMT 11
Calling all Witchdoctors .... The price on your exhaust from Southport Exhausts. Did that include a muffler ?
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Post by francesco on Jan 17, 2005 17:23:11 GMT 11
I aint a witchdoc .........but i can tell you it did  |
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Post by caffa on Jan 23, 2005 1:23:19 GMT 11
LOL. Thanks for that
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Post by Jimmu on Mar 13, 2005 16:31:32 GMT 11
Did you guys get it Mandrel bent?
Reccomend anyone in Brisbane?
Jimmy
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Post by francesco on Apr 5, 2005 18:54:40 GMT 11
I called Southport exhausts today....they said that they have had to do price increase due to demand on steel (steel prices probably gone up due to tank making ) so what was a $290 job for 2.5 inch system with flexi joint and resinator now costs $350. I found a place up the road from where I work that will do it for $400.....so I might just go there.....would cost me more than that just in the inconvenience. |
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Post by Jimmu on Apr 5, 2005 19:47:58 GMT 11
Where did you go francesco?
Southport exhausts wuoted me 400 -450 for a 2.5 mandrel bent from the turbo back.
But I would prefer to take it somewhere closer.
Is the 400 price Mandrel bent?
I am ready to get it done as soon as I find someone to do it.
We may get it a bit cheaper if we get two of them done...
Jimmy.
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